Flame electrode control device



Aug. 31, 1948.

J. O. ROSCHE FLAME ELECTRODE CONTROL DEVICE Filed April 18, 1945INVENTUI? Jon 0105015 flfrfllflvf) Patented Aug. 31, 1948 FLAMEELECTRODE coN'rnoL DEVICE JohnO. Rosche, Minneapolis, Minn asslgnor toMinn 'eapolis-Honeywell' Regulator Company,

Minneapolis, Minn., a corporation ofDelaware Application April 18, 1945,Serial No. 588,960

My invention is generally related to a combustion control device. Oneparticular use of the arrangement is'in conjunction with 'a flamedetecting mechanism used in an electrically operated combustion systemand comprising a flam detecting electrode. g

Flame detecting mechanisms are well known and their function is unrstood by persons skilled in the art. In brief, devices of thisparticular nature are positioned in the combustion area of a furnace orthe like so that a flame may impinge upon a portion of the device. Theelectron conducting property of the flame is utilized to complete anelectric circuit which will include the detecting mechanism andgenerally the burner from which the flame is issuing. The relativelysmall current so conducted is then greatly amplified and utilized as acontrol impulse for operating mechanisms associated with the properoperation of the furnace or the like.

' The previously known devices generally consisted of a metal rod whichserved as an electrode and was insulatingly mounted in the side of afurnace with the rod extending to a point adjacent the burner. After aperiod of use, and particularly when the device is used in conjunctionwith an oil burning furnace, a deposit of the products of combustionwill. form on the rod and its supporting structure in such a manner asto provide a conduction path between the electrode and its supportingstructure or the body of the furnace, both of which are usuallyconnected through ground to the burner.

In certain flame detecting apparatus of this general nature, acontinuous deposit of the prod- .ucts of combustion between theelectrode and other flame detecting apparatus is designed to distinguishbetween a flame and a short circuit;

in this case the short circuit usually causes the flame detecting,apparatus to'be maintained in a condition normally assumed when there isno flame even though a flame be actually present thereby causing a lessdangerous but troublesome culty in either type of apparatus, it wascustomary to mount the electrode in a long pipe or tube to impede thedeposition of these combustion 5Claims. (01.158 28) products-between theelectrode and the supporting member. However, when the deposition wasthe result-of a minor explosion or blow-back it ternal surfaces of thetube in such a manner as to form a -conduction path between the elecafunctioning of the furnace. To off-set this diffitrode and the supportand thereby defeat the purpose of the tube.

To completely overcome this difllculty, the present device isconstructed with a protector which is mounted in relation to theinsulator and the electrode to prevent the formationof I such acontinuous layer of the products of combusiion which may result aseither a gradual accumulation or a rapid deposition which might resultfrom a blow-back. The protector is constructed in the form of acup-shaped baflle whichis mounted on the insulator and in electricalcontact with the electrode, but positioned so that theclosed end of thecup-shaped protector extends in the direction of the combustion area,while the open end of the cup-shaped protector surrounds the insulatorfor a substantial distance in such a manner that it is neither incontact with 'the insulator nor the supporting structure. Thus it willprevent -a direct deposition of the products of combustion over theentire length. of the insulator and it also provides. an enclosed airpocket about the insulator which forms a compressible air cushion toprevent the products of combustion from entering the enclosed portionbetween the protector and the insulator.

The principal object of the invention is to provide an arrangement formounting a flame detecting electrode in a supporting structure in such amanner as to prevent the deposition of a. continuous layer of theproducts of combustion having conducting properties from forming betweenthe electrode and the supportingmember.

Another object isto provide means for mounting an electrode within afurnace with a protector that forms a compressible air. cushion around aportion of the electrode supporting structures, so as to prevent theformation of a short circuiting, layer of substances resulting fromcombustion within the furnace.

Other and further objects may become apparent from the followingdescription and claims and in the appended drawing in which the singlefigure is a cross-sectional view of the assembly with certain partsbroken.

' Referring now to the drawing, the device consists of a metallicelectrode H! which is mounted within a casing member indicated by thegeneral refe'rencenumeral H. The casing II is adapted to be threadedlydisposed on a nipple l2 which is suitably fastened as by welding in thewall of ,a furnace, indicated by the reference numeral IS, in such amanner that a flame |4 issuing from a burner pipe l5 will impinge on aportion of the electrode Ill.

The casing II has a tubular shank portion l6 which is provided with aninwardly disposed threaded portion ll, adapted to cooperate with thethreads on the nipple l2. At its other end, the shank portion I6 isprovided with a flange |8, in which are'disposed a number of screws I!)for supporting a cup-shaped -member 20 against the flange It! by aplurality of key hole slots, not shown. One or more apertures 2| areprovided in the cup-shaped member 20 to provide for the passage ofconductors to the electrode. A cap member 22 is provided to befrictionally engaged on the open end of th cup-shaped member 20 toenclose the same.

A spacing adapter 23 is threadedly disposed within the flanged portionof the shank I6 to support an assembly of parts. A ceramic tube 25,preferably formed of Pyrex, is positioned within the adapter and sealedthereto by a cement ring 24 which is introduced in a fluid form' betweenasbestos washers 24a, 24b and permitted to solidify as a sealing means.A metallic tube 26 is located within the Pyrex insulator 25 in such amanner that it engages and supports the electrode ill. The metallic tube26 is fastened to the insulator 25 by a soft washer 21, a metallicwasher 28, and a nut 29, which is threaded on the outer periphery of thetube 26. A connecting adapter 30 having an internal thread and providedwith a compressible washer 3| surrounds both the electrode l and thetube 26 in such a manner that when it is turned on the threaded portionof the tube 26, the adapter will firmly engage the electrode [0 withinthe assembly. By loosening adapter 30 on tube 26, the electrode Illwhich is held in place by pressure on the soft washer 3|, may be readilyremoved through the rear of the adapter without removing the casing IIfrom the furnace wall.

,A protector in the shape ofv a cup-shaped baille 35 surrounds a portionof the insulator 25 within the shank 6 so as to form a partiallyenclosed air layer about the insulator 25. The protector 35 is fastenedto the tube 26 by spinning or swaging and is separated from theinsulator 25 by a soft insulating washer 36. This bailie or protector 35constitutes a vital part of the device and is constructed to prevent theformation of a continuous layer of soot between theelectrode l0 and anyof-the metallic parts of the casing indicated by the general referencenumeral H in such a manner that current conducted by the electrode couldbe short circuited to the casing. Current is conducted from theamplifier 40 through conductor 4| to the adapter 30, whence it travelsthrough the electrode It). In the event the flame I4 is existent,current will be conducted through it to the burner whence it returns tothe amplifier through conductor 42. The flame i4 and burner l5 are shownmerely'as an example to illustrate the electrical path and in actual usemay be either an oil burner or a gas pilot. In actual use, the electrodel0, which is shown as being broken, may extend into theifurnace for asufficient distance to beadjacent the combustion area.

When in operation, the combustion process within the furnace willproduce waste products which are normally of a gaseous nature and whoseescape is provided for by the exhaust flue. When oil is used as a fuelit frequently happens that through incomplete combustion a portion ofthe hydrocarbons are not completely consumed and the gases becomeladened with a carbonaceous soot. Not all of the soot will escapethrough the flue and this portion will tend to settle on the surroundingwalls and portions of the furnace. The flame detecting mechanism whichis normally positioned in a side wall of the furnace is equally subjectto the deposition of. soot along with other interior parts of thefurnace. However, if' a continuous layer of soot forms on the electrodeand its supporting structure this will result in th undesirable shortcircuit previously mentioned. Under normal operation, only a relativelysmall amount of the soot ladened gases will enter the device and thissoot will principally deposit on the exterior of the bailie. However, attimes, and due to delayed ignition, aminor explosion may occur forminggases which contain a relatively large amount of soot. These gasesexpand rapidly and will force themselves in all directions. Under theseconditions, the gases entering the device are initially retarded by thefact that the enclosure is sealed, but the soot will nevertheless bedeposited on the interior walls of shank IS, the exterior of battle 35,and to a structur I From the foregoing,-it should be evident that Ihave, by this arrangement, mounted a conducting electrode within acombustion furnace in such a manner that it may be readily removed forreplacement, and a particular featureof the device is that the productsof combustion cannot deposit themselves between the electrode and itssupporting structure in such a continuous manner as to provide a shortcircuit for the current conducted by the electrode. As my invention mayassume different shapes and proportions, I do not wish to be limited bythe single disclosure, but rather by the terms of the appended claims.

I claim as my invention:

1. In a combustion indicating device, in combination, an electrode forconducting current in a circuit which includes a flame, means forinsulatingly supporting a portion of said electrode adiacent acombustion area, and means for preventing formation of a continuousconducting deposit of the products of combustion between said electrodeand said supporting means, said means including a hollow cylindricalmember surrounding said supporting means in spaced relation and sealedthereto at the end nearer the combustion area to form a. static airpocket in cooperation with said supporting means.

2. In a device or the class described, a housing structure adapted to bemounted in communitubular protecting baffle surrounding said insulatorin'spaced relation thereto and formed at one end to engage saidinsulator to form a sealed junction with said insulator with the sealedend extending in the direction of the combustion area, said baillecooperating with said insulator to form a static air pocket to preventdeposition of residual combustion products on the surface of saidinsulator enclosed by said baffle.

3. In a device of the class described, a housing structure adapted to bemounted in communication with the combustion area of a furnace, aconducting electrode adapted to be mounted within said housing andextending into the combustion area of said furnace, an insulatorsupportingly surrounding a portion of said electrode to electricallyisolate's'aid electrode from said housing, and a hollow cylindricalbaflle surrounding a portion of said insulator in spaced relation andsealed thereto at the end adjacent the combustion area of said furnace,said baflle cooperating with said insulator to form a static air pocketoperable to prevent the deposition of the residual products ofcombustion upon the entirety of said insulator exposed to the combustionin said furnace.

4. In a device of the class described, a housing structure adapted to bemounted in communication with the combustion area of a furnace, acurrent conducting electrode, an insulator, said insulator surroundingan end portion of said electrode and insulatingly supporting the endportion of said electrode within said housing, and a, hollow cylindricalmember having an inner diameter larger than the outer diameter of saidinsulator ber and said insulator forming a static air pocket to preventthe deposition of the conducting ressymmetrically spaced about saidinsulator and 35 sealed thereto at the end of said member facing thecombustion area of said furnace, said memidueof combustion products upona portion of said insulator.

5. In combination, a hollow housing structure adapted to be mountedin-communication with the combustion area of a furnace, a currentconducting electrode, coupling means, an insulator, said insulator beingmounted within said housing, having an outside'diameter less than theinside diameter of said housing, surrounding an end portion of saidelectrode, and sealed at one end of said housing by said coupling meansto form a, forwardly facing static air pocket, a hollow cylindricalmember having a mean diameter less than the inside diameter of saidhousing but greater than the outside diameter of said insulator andsealed to said insulator at the end of said member closest to thecombustion area of the furnace, said member and said insulatorcomprising a rearwardly facing static air pocket within said forwardlyfacing pocket to prevent the deposition of residual combustion productson the surface of said insulator within said rearwardly facing pocket.

' JOHN O. ROSCHE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Yates May 12, 1942

